Suction cleaner control



Feb. 27, 1951 0, w, TIMM 2,543,343

SUCTION CLEANER CONTROL Filed March 5, 1946 56 FOI? THE FZQM A Tropffys Patented Feb. 21, i951 'SUCTION CLEANER OONTBOL th W. 'limnnvan N limmAireraftCorporatio aoorporationolcalifornia Ul Calif.. assigner to n, Van Nuys, Calif.,

annum mma s. me. serai No. 652.152

u cum. (c1. iss-s4) My invention relates to the suction cleaner art and. more particularly. to a suction cleaner adapted for household or hotel use or the like and having a number of improvements over standard types of such devices. Specifically, the present invention pertains to an improved means for controlling the operation of suction cleaners of the type disclosed in my prior application for United States patent entitled "Suction Cleaner With Switch Circuit, Serial No. 611,787, filed August 2l, 1945.

It is common in the art to provide a vacuum cleaner oi the suction type with a motor and a dust collecting chamber enclosed in a housing, the device having supporting runners and adapted to be moved from place to place in operation by a suction hose connected to the suction opening of the device. Such suction cleaners commonly are provided with the motor and dust chamber in horizontal axial alignment, which provides a very low construction which is awkward for an operator to pick up, as must frequently be done in moving the device from room to room for operation. It is therefore an object of my present invention to provide a wholly enclosed suction cleaner of sufllcient height to permit the handle thereof to be grasped by an operator without requiring a substantial stooping movement of the operator, thus relieving the physical eiort required to move many of the suction cleaners of the prior art. I prefer to accomplish this object by providing an enclosed housing separated by a partition into a vertical motor chamber and a vertical filter chamber, a motor and fan unit being disposed in the motor chamber and a vertical illter bag being disposed in the filter chamber, and this is a further object of the invention.

Still another object of my invention is to provide a suction cleaner in which dust and foreign materials are ltered from incoming air on the outside of a suitable lter bag, with improved means provided for agitating the bag as desired to remove vdust therefrom and thus clean the filtering surface.

motor for agitating a filter bag to remove dust from the filtering surface thereof, an electric circuit whereby the auxiliary motor is energized only when the main motor is de-energized. I prefer to provide such a circuit whereby the auxiliary motor is so energid for a predetermined period and then is automatically de-energized. and this is another object of the invention.

A still further object of ymy invention is to provide. a suction cleaner of the type referred to in which the momentary operation of the auxiliary motor for agitating the lter bag is controlled by the degree of suction occurring in the suction cleaner, in addition to the de-energization of the main motor, so that the initiation of operation of the auxiliary motor will be delayed until the degree of suction is reduced to a predetermined value to thus control the period of operation of the auxiliary motor.

Other objects of the invention reside in additional construction features to be pointed out hereinafter, and will be evident from the following specification and the drawing, which is for illustrative purposes only and in which:

Fig. l is a longitudinal vertical view, partly in cross section, taken through my suction cleaner;

Fig. 2 is a side elevational view of the improved controlling device of my invention, partly in section and showing the device connected in the electric circuit which is shown diagrammatically; and

Fig. 3 is a view similar to Fig. 2 showing the contacts of the controlling device closed to effect energization of the circuit for the auxiliary electric motor.

Referring to the drawing, I show a housing I0 divided by a vertical partition wall i2 into a Y motor chamber I3 and a filter chamber i4. the upper ends of which communicate through an upper chamber i5 of the housing. Disposed in the motor chamber i3 is an electric motor i1, constituting the main motor unit of the invention, and disposed in the filter chamber il is a lter unit i8.V

The electric motor i'l is vertically disposed in the motor chamber i3, being supported by a bearing Ii on a circular plate 20, which in turn is supported by a resilient rubber washer 2| on the upper end of a reel shaft 22 which engages a detachable bottom wall 23 of the housing il. The electric motor il is enclosed by a cylindrical porous lter element i9. The upper end of the electric motor il is provided with an annular collar 2i which engages an annular sealing ring 23, preferably formed of rubber or other 'resilient'material, which in turn engages an annular collar 21 formed on a horizontally disposed flange 23 which is suitably secured to the inner wall of the housing I3 and to the partition wall I2, as by welding or otherwise. As will be evident. the rubber washer 2| and the sealing ring 23 provide a resilient mounting for the electric motor I1, adapted to absorb vibration thereof. As will also be understood, the drive shaft (not shown) of the electric motor I1 extends downwardly into the vertical filter element I9 and is provided with suitable fan blades (not shown) thereon adapted to draw air from the upper chamber I5 and through the motor chamber |3 to expel it from a suitably disposed discharge opening 29 formed in the lower portion of the housing I3, the filter element I9 removing any traces of dust from the air circulated therethrough.

In the motor chamber I3 beneath the electric motor I1` is a reel device 3|, which may be of any form well known in the art, which is rotatably mounted on the reel shaft 22 and is adapted to carry a power cord 32, one end of which extends out of the housing through a suitable power cord opening 33, the power cord being of the conventional form consisting of two wires 34 and 35, one of which is connected electrically to an inner collector ring 33 and the other of which is electrically connected to an outer collector ring 31, as is well known in the art. The collector rings 33 and 31, which are fixed to the reel device 3| and rotate therewith relative to the housing i3. are engaged by conventional brushes 33 and 39, respectively. The brush 33 is connected by a wire 4| to a pole of a single-pole, double-throw main switch 42, as best shown diagrammatically in Fig. 2, the contacts of which are connected by wires 43 and 44 to an auxiliary switch 45.

The auxiliary switch 45 may be mounted within the suction cleaner housing I3 in any manner and preferabbr it is secured to the side of the main electric motor I1 as shown in Fig. 1. The auxiliary switch 45 includes a housing 41 constructed from dielectric material and provided with electrical contacts 48 and 49 to which 'the wires 43 and 44 are connected, respectively. The housing 41 is also provided with electrical contacts 53 and 5|. The contacts 49 and 5| are connected by a resistance wire 52, which, when current is flowing therethrough, is designed to heat a bimetal strip 53 connected to the electrical contact 48 so as to flex the bimetal strip 53 to adapt a contact 54 thereon to engage the lower end of a'contact screw 55 electrically connected to the electrical contact 53. The housing 41 isA provided with an aperture 55 in its lower side to receive the cylindrical portion 53 of a member 51. The member 51 has a peripheral flange 59 adapted to abut the lower surface of the housing 41 and the flange may be held thereagainst by the head of a screw 63 threaded into a tapped hole in the lower portion of the housing. Below the flange 59, the member 51 is provided with a reduced stem 3l. The member 51 has an axial bore 32 and a counterbore 33 in its upper end, said counterbore constituting a cylindrical suc-l tion chamber. A flexible tube 35 has one of its ends enclosing the stem 3| of the member 51 and its other end joined to the end of a tubular sleeve 53 having external threads and passing through a hole in the ilange 23 of the housing I3. Nuts 31 and 63 screwed onto the threads of the sleeve 33 and set up against the opposite sides of the flange 23 serve to secure the sleeve in place. It is apparent from the above that the chamber 33 of the member 51 will be subjected to suction created within the chamber I3 when the main motor I1 is in operation. Arranged to slide axially in the suction chamber 33 is a piston 13 having an upwardly projecting piston rod 1|. 'I'he rod 1| extends upwardly through an elongated opening 12 in the bimetal strip 53 and its end is flattened to provide a head 13 adapted to engage the upper surface of the bimetai strip to depress the strip when suction is created in the chamber 33.

'I'he electrical contact 53 is connected by a wire 14 to one side of an auxiliary electric motor unit 15. the other side of which is connected by a wire 13 to the brush 39, the brush 39 also being connected by a wire 11 with one side of the main electric motor I1. The other side of the main electric motor I1 is connected by a wire 1I to the electrical contact 5| of the auxiliary switch 45.

Integrally connected with the top of the vertical partition ywall I2 is a horizontal plate 33 provided with a rectangular opening 3|, the inner edge of the plate being curved to form a lip 32 adapted to be engaged by a sealing ring 33, preferably formed of rubber or other resilient material, which is supported in a cupped ange 34 of rectangular shape, which, together with the sealing ring 33, closes the rectangular opening 3|, the flange being provided with openings 35 and `35 at each end thereof and being secured to the auxiliaryv electric motor unit 15, preferably by screws 31.

The auxiliary electric motor unit 15 is of any suitable design, including a vertical drive shaft 33 and an electric motor (not shown in detail). The auxiliary electric motor unit 15 is provided with a pair of electrical contacts 39 and 93 supported on insulated contact arms 9|, the electrical contacts 39 and 93 being adapted to engage contacts 9| and 92 supported by a bracket 93 suitably secured to the inner wall of the top of the housing I3, the contacts 9| and 92 being electrically connected to the wires 13 and 14, respectively. The auxiliary electric motor unit 15, together with the cupped flange 34 secured thereto, is suspended by means of a screw 94 from the housing I3. It will thus be observed that upon removal of the screw 94 and the removable bottom wall 23, the filter unit I3 may be removed downwardly through the housing I3, which breaks the electrical connection between the contacts 39 and 9| and the contacts 93 and 92, to permit the auxiliary electric motor unit 15 and its associated mechanism to be readily removed from the housing for cleaning or repair, and this is a feature of the invention.

Secured to and depending from the cupped flange 34 is a bag member 95, comprising a portion of the filter unit I3, and preferably formed of a nlter. fabric material suitable for filtering dust and dirt from air passing therethrough. Disposed in the hollow bag member is the agitating means 33 of the invention, which includes a framework 91 consisting of four vertical members 93 interconnected by four brace members 99, the lower ends of which aresecured to a rectangular flange member |33 having a circular central opening |3| therein. The members 93 and 99 are preferably made of resilient material, such as spring steel, and the upper ends thereof are secured tofour depending ears |33 ingverticalendmeuibersIandlllandapair of bottom straps |01. As will be apparent, the agitator elementi is spaced but slightly from tbeinnerwallofthebagmemberl.sothat upon lateral movement of the agitator element it will contact the bag member to agitato the Salle.

Connected to the drive shaft 00 of the auxiliary electric motorunit 10 by a resilient coupling |00. preferably formed of rubber or other resilient material. is a vertical rotatable shaft IIO which passes through a bearing III and has secured to the lower end thereof a crocs-pin III, to the outer end of which is fastened an eccentric weight lil. The bearing III is supported in a resilient diaphragm Ill, preferably formed of rubber or other resilient material, which snaps into the central openingl IOI of the rectangular flange member |00.

Disposed in the filter chamber Il below the filter unit I0 is a removable tray I I0 which passes through a rectangular opening I i1 in the housing I0. Also communicating with the filter chamber I4 is a suction opening III. and between the suction opening IIB and the filter unit I0 is disposed a deection plate member I Il which directs air entering the filter chamber around the inner wall thereof and prevents it from impinging directly upon the bag member 05.

In operation, which will be best understood by preliminary reference to Fig. 2, when the main switch 42 is closedy so as to close the circuit between the wires 4I and 44, current ows therethrough. through the resistance wire l2. and the wire 10 to the main electric motor I1 to energize the same, the other side of the motor being at all times connected by the wire 11 to the power supply. When the main electric motor I1 is energized, "the, blower unit connected therewith (not shown) draws air through the suction opening III into the filter chamber Il. through the lter unit Il to filter all dust and dirt particles therefrom. through the upper chamber I and the motor chamber I3, through the motor I1, and forces lt through the filter element Il and out through the dischargev opening 20.

As will be apparent, when the main electric motor I1 is thus energized, current flowing through the resistance coil 52 will cause it to heat the bimetal strip 00. Heating of the bimetal strip tends to flex it upwardly to cause its contact I4 to approach the lower end of the contact screw 5S. However, such flexing is resisted by the pistonv which, after the main motor I1 has been started and suction created in the chamber Il, is

'drawn downwardly under the influence of suction effected in the tube 05 and suction chamber 00. It is thus seen that the contact M of the bimetal strip Il is withheld from engagement with the lower end of the contact screw il during the entire operation of the main motor i'l. `It

will also be understood that so long as the main switch 42 remains in its closed position above described. in which the main electric motor I1 is energized, no curren will now through the switch 46 i ergised the main electric motor II for a sumcient period of time to heat the bimetal strip 00. the

wirewillbeconnectedtothewirell topermit' electric current to pass through the contact ll to the bimetal strip. As the speed of the main electric motor is retarded. the degree of suctionv in the chamber I0 will gradually lessen and eventually the suctional pull exerted upon the piston 10 will become less than the tension of the heated bimetal strip B0. When this condition exists the bimetal strip I3 will be permitted to ilex upwardly to cause its contact. to engage the lower end of the contact screw Il as shown in Ilig.` 3, thereby completing the circuit to the auxiliary electric motor unit 15 through the wire 14. Since the other side of the electric motor unit 15 is connected at all times to the other side of the main power supply by the wire 10, the electric motor unit 1l will be energized.

Energization of the auxiliary electric motor 15 causes rotation of its vertical drive shaft 00 and, through the coupling |09, the rotatable shaft I I0. The eccentric weight H3 unbalances the rotating shaft H0, causing it to oscillate the agitator element |04 to cause the element to sharply engage andA agitate the inner wall of the bag member 95. Buch agitation of the bag member shakes the dust accumulated on the outside thereof, the dust settling into the removable tray IIB..

Cooling of the resistance wire 52, due to the de-energizing thereof, allows the bimetal strip 53 to cool, and after a. relative short predetermined period of time, for example, three to five seconds, the bimetal strip moves downwardly thus breaking electrical contact between the contact 54 and the contact screw 55, which opens the circuit to the auxiliary electric motor unit 15 to de-energize the same.

The cycle of operation just described is of primary importance in the invention, although it is to be understood that it may be modified without departing from the spirit of the invention. Due to the relatively small surface area of the bag member 95. it will rapidly become clogged with dust during operation unless the dust is removed therefrom at relatively frequent intervals. Although separaie manually operable switches may be provided for the main electric motor i1 and the auxiliary electric motor unit 15, I have found that the average housewife will either forget to operate the auxiliary motor at sufficiently close intervals to maintain the surface of the bag member 05 adequately free from dust, or will merely neglect to do so, or will operate it for an unnecessarily long period when she does operate it.l Since in normal household use an electric suction cleaner is frequently energized an'd de-energized, and since in my invention the bag member 05 is agitated every time thatI the main motor is deenergized, it will be apparent that dust deposited on the outer surface of the bag member will be shaken of! and collected in the tray IIS almost as soon as deposited on the bag member, thus maintaining the bag member adequately pervious to the air stream flowing therethrough. Also, since the auxiliary electric motor unit 15 is actuated in each instance for a predetermined time interval, it is insured that the bag member 95 is shaken sufficiently to accomplish this purpose, fbut substantially no more. Thus, the present inl vention provides means forautomatically maintaining the filter unit I0 in satisfactory operating condition over long periods of use, the only reu quirement on the user being that the tray IIO I to oscillate smoothly in response to the unbalanced oscillation of the rotatable shaft III caused by the eccentric weight III, which contributes to the desired result.

As an outstanding feature of the present. invention, the actuation of the auxiliary switch 4l is controlled by two factors, i. e., the de-energization oi the main electric motor i1 and also the suction created within the suction chamber Il of the suction cleaner. Through the provision oi the suction controlled piston 1l the closing of the auxiliary electric circuit is delayed until such time as the-suction created by the fans driven by the main electric motor I1 is substantially reduced to insure vthat the bag member 9e will be agitated only after a suction cleaning operation has been completed. 'I'he suction piston 10 further serves to reduce the period of agitation of the bag member Il to a minimum so that excessive operation of the agitation means 06 is avoided. The improved auxiliary switch 45 constitutes an important improvement over a similar auxiliary switch disclosed in my prior application, referred to previously, vand employing a bimetal strip as the sole means for closing and opening the circuit to the auxiliary electric motor and in which the periodo! energization of the auxiliary motor unit is dependent entirely upon the heating and cooling of said bimetal strip.

It will be apparent to those skilled in the art that many of the elements of my device. as illustrated and described hereinabove, may be replaced by other elements having substantially the same mode of operation without departing from the spirit of my invention, and consequently I do not desire to be limited to the speciilc form illustrated and described, but desire to be aiorded the full scope of the followingl claims.

I claim as my invention:

= 1. In a suction cleaner, the combination of: lan enclosed housing having a suction opening operative to control the duration oi' energization of said auxiliary motor.

2. In a suction cleaner, the combination of: an enclosed housing having a suction opening and a discharge opening; lter means in said housing between said openings and adapted to iilter air passing therebetween; a main electric motor device in said housing and adapted when energized to create suction in said housing to move air between said openings and through said iilter means; an auxiliary electric motor in said housing and adapted when energized to agitate said filter means; an electrical circuit tor said main motor device; means for energizing said main motor device; means controlled by the suction in said housing for energizing seid suxiliary motor automatically; and means in said circuit operative automatically upon de-energization oi said main electric motor device for maintaining said auxiliary electric motor energized for a predetermined period of time after said main motor device is de-energized.

3. In a device of the character described, the

combination oi: filter means tor filtering a ilow o! air passing therethrough: electrical power means for creating suction within said device tocause anow oiairthroughsaidilltermeans; electrical agitating means for agitating said nlter means; means for 'electrically energizing saidpowermeanstocauseailowotairthrough said iilter means; energizing means for automatically energizing said electrical agitating means after said power means is de-energised: and means electrically connected to said power means for controlling the duration of energizetion ci said energizing means, said suction responsive means being adapted to withhold said energizing means from operation until the suction in said device is substantially reduced.

4. In a device oi the character described. the combination of: filter means for filtering a iiow of air passing therethrough; electrical power means for creating suction in said device to cause la'ilow of air through said niter means; electrical agitating means for agitating said iilte'r means; means for electrically energizing said power means to cause a flow oi air through said illter means; means responsive to the suction in said device i'or automatically energizing said electrical agitating means; and thermal means electrically connected to said power means and operative to maintain said energizing means energized ior a predetermined period o! time after said power means is de-energizcd.

5. In a device ot the character described. the combination of: nltermeans for nltering a ilow of air passing therethrough; electrical power means for creating suction in said device to cause a now of air through said nlter means; electrical agitating means for agitating said illter `means; a nrst electrical circuit adapted to supply current to said power means; a second electrical circuit adapted to supply current to said agitating means. said second circuit including switch means; means responsive to suction within said device tor closing said switch means; and thermal means in said ilrst electrical circuit for opening said' switch after a predetermined period of time.

6. In a device of the character described, the combination oi: illter means for nltering a flow of air passing therethrough; electrical power means for creating suction in said device to cause a now o! air through said nlter means; electrical agitating means tor agitating said illter means; a nrst electrical circuit adapted to supply current to said power means, including a.l main switch; and a second electrical circuit connected to said main switch and adapted to supply current to said agitating means. said 'second circuit including auxiliary switch means. said ilrst and second circuits being adapted to be selectively energizedby operation oi' said main switch; and means responsive to suction in said device for delaying'the energization of said second circuit by said auxiliary switch means until the suction has been reduced to a predetermined value.

auas

land a discharge opening; filter means in said housing between said openings and adapted to 'filter air passing therebetween; a main electric motor'device in said housing and adapted when energized to ycreate suction in saidhousing'to move air between said openings and through said nlter means; an auxiliary electric motor in said housing and adapted when energized to agitate said filter means; a first electrical circuit connected with said main electric motor means and adapted' to supply current thereto, including a main switch; a second electrical circuit connected with said auxiliary electric motor and adapted to supply current thereto; including auxiliary switch means; switch closing means adapted to be operated in response to flow of current through said first circuit to close said auxiliary switch means: and means responsive to suction in said housing for withholding said switch closing means from operation until the suction in saidV housing is substantially reduced following de-energization of said nrst circuit.

8. In a suction cleaner. the combination of: an enclosed housing having a suction opening and a discharge opening: lter means in said housing between said openings and adapted to lter air passing therebetween; a main electric motor means in said housing and adapted when energized to create suction in said housing to move air between said openings and through said lter means: an auxiliary electric motor in said housing and adapted when energized to agitate said filter means: a first electrical circuit connected with said main electric motor means and adapted to supply current thereto, including a main switch; a second electrical circuit connected with said auxiliary electric motor and adapted to supply current thereto, including auxiliary l switch means. said auxiliary switch means being of the thermally responsive type; switch closing means responsive to flow of current through said first circuit when said main switch is closed and adapted to close said auxiliary switch means; and means responsive to suction within said housing for withholding said switch closing means from operation until the suction in said housing is reduced to a predetermined value following de-energization of said main motor.

v9. in a suction cleaner, the combination of: an enclosed housing having a. suction opening and a discharge opening; filter means in said housing between said openings and adapted to lter air passing therebetween; a `main electric motor means in said housing and adapted when energized to create suction in said housing to move air between said openings and through said filter means; an auxiliary electric motor in said housing and adapted when energized to agitate said filter means; a first electrical circuit connected with said main electric motor means and adapted to supply current thereto, including a main switch; a second electrical circuit connected with said auxiliary electric motor and adapted to supply current thereto; auxiliary switch means included in said second electrical circuit, said auxiiary switch means including a thermally controlled element connected in said first electrical circuit and responsive to a flow of current through said first circuit to adapt itto close said second circuit when said main switch is opened; and a second element connected to said thermally controlled element and responsive to suction within said housing for withholding said thermally con- .trolled element from operation until the suction within said housing is reduced to a predetermined value following de-energizing of said main electric motor means.

10. In a suction cleaner, the combination of: an enclosed housing having a suction opening and a discharge opening; filter means in said 'housing between said openings and adapted to filter air passing therebetween; a main electric motor means in said housing and adapted when energized to create suction in said housing to move air between said openings and through said filter means; an auxiliary electric motor in said housing and adapted when energized to agitate said filter means; a first electrical circuit connected with said main electric motor means and adapted to supply current thereto, including a main switch; a second electrical circuit connected with said auxiliary electric motor and adapted to supply current thereto; auxiliary switch means connected in said second electrical circuitv and including a stationary contact element and a thermally controlled contact element adapted when heated to engage said stationary contact element to close said second circuit, said main switch being movable to a first position to close said first circuit and to a second position to supply current to said thermally controlled contact element; a heating element included in said rst circuit and adapted to heat said thermally controlled contact element when said rst circuit is closed; and means responsive to suction within saidv housing for withholding said thermally controlled contact element from engagement with said stationary contact element until said suction is reduced to a predetermined value following movement of said main switch from said first position to said second position.

11. In a suction cleaner, the combination of an enclosed housing having a suction opening and a discharge opening; filter means in said housing between said openings and adapted to filter air passing therebetween; a main electric motor means in said housing and adapted when energized to create suction in said housing to move air between said openings and through said filter means; an auxiliary electric motor in said housing and adapted when energized to agitate said filter means; a first electrical circuit connected with said main electric motor means and adapted to supply current thereto, including a main switch; a second electrical circuit connected with said auxiliary electric motor and adapted to supply current thereto; auxiliary switch means connected in said second electrical circuit and including a stationary contact element and a thermally controlled contact element adapted when heated to engage said stationary contact element Y to close said second circuit, said main switch being movable to a first position to close said first circuit and to a second position to supply current to said thermally controlled contact element; an electrical resistance element included in said first circuit and adapted to heat said thermally controlled contact element when said rst circuit is closed; and suction responsive detaining means connected to said thermally controlled contact element and operated by suction within said housing to withhold said thermally controlled contact element from engagement with said stationary contact element during normal operation of said suction cleaner, said suction responsive means being adapted to release said thermally controlled contact element when said suction is `reduced to a predetermined value following move- 11 ment of said main switch from said first position to said second position whereby to permit said thermally controlled contact element to engage said stationary contact element to close said second circuit.

12. In a suction cleaner, the combination of: an enclosed housing having a suction opening and a discharge opening; filter means in said housing between said openings and adapted to filter air passing therebetween; a main electric motor means in said housing and adapted when energized to create suction in said housing to move air between said openings and through said filter means; an auxiliary electric motor in said housing and adapted when energized to agitata said filter means; a first electrical circuit connected with said main electric motor means and adapted to supply current thereto, including a main switch; a second electrical circuit connected with said auxiliary electric motor and adapted to supply current thereto; auxiliary switch means connected in said second circuit and including a stationary contact element and a thermally controlled contact element adapted when heated to engage said stationary contact element to close said second circuit said main switch being movable to a first position to close said iirst circuit and to a second position to supply current to said thermally controlled contact element; an electrical resistance element included in said first circuit and disposed adjacent said thermally controlled contact element to heat the same when said first circuit is closed; a tubular member having walls defining a suction chamber; a piston adapted to move in said chamber and connected to said thermally controlled contact element; and a tubular conduit communicating between said suction chamber and the interior of said housing between said suction opening and said discharge opening to subject said piston to suction during normal operation of said suction cleaner to withhold said thermally controlled contact element from engagement with said stationary contact element, said piston acting to release said thermally controlled contact element when said suction is reduced to a predetermined value following movement of said main switch from said first position to said second position whereby to permit said thermally controlled element to engage r said stationary contact element to close said second circuit during the period of time in which said thermally controlled contact element remains heated.

13. In a suction cleaner, the combination of: an enclosed housing having a suction opening and a discharge opening; filter means in said housing between said openings and adapted to filter air l2 passing therebetween; a main electric motor means in said housing and adapted when energized to create suction in said housing to move air between said openings and through said filter means; an auxiliary electric motor in said housing and adapted when energized to agitate said filter means; a first electrical circuit connected with said main electric motor means and adapted to supply current thereto, including a main switch; a second electrical circuit connected with said auxiliary electric motor and adapted to supply current thereto; auxiliary switch means connected in said second circuit and including a casing; a contact screw adjustable in said casing; a thermally controlled contact strip in said casing and adapted when heated to engage an end of said contact screw to close said second circuit, said main switch being movable to a first position to close said first circuit and to a second position to open said first circuit and supply current to said contact strip; an electrical resistance element disposed within said casing adjacent said contact strip and included in said first circuit, said resistance element being adapted to heat said contact stripwhen said first circuit is energized; a member on said casing having walls defining a suction chamber; a piston adapted to move in said chamber and connected to said contact strip; and a tube extending between said suction chamber and the interior of said housing between said suction opening and said discharge opening to subject said piston to suction during normal operation of said suction cleaner to withhold said contact strip from engagement with said contact screw, said piston being adapted to release said contact strip when said suction is reduced to a predetermined value following deenergization of said first circuit by said main switch whereby to permit said contact strip to then engage said contact screw to energize said second circuit during the period'of time in which said contact strip remains heated.

OTTO W. TIMM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I EN'IS Number Name Date 946,535 Craver Jan. 18, 1910 1,493,789 Mullen May 13, 1924 1,715,273 Billings May 28, 1929 2,318,395 Hornbrook May 4, 1943 2,372,944 Forsberg Apr. 3, 1945 2,443,162 Hallock June 8, 1948 

